Re: Implementing a smart pointer which works with incomplete types

James Kanze <>
Sun, 2 Mar 2008 15:12:33 -0800 (PST)
On 2 mar, 20:43, Juha Nieminen <nos...@thanks.invalid> wrote:

James Kanze wrote:


The only situation which I can think of where it may not work
is when 'SomeOtherClass' has no constructor (or, more
precisely, it only has the default compiler-generated
constructor). AFAIK that's the known limitation of the
technique: The constructor of the class which has that type of
smart pointers as members must be explicitly implemented.

Why is that limitation present? If the class is defined (i.e.
the class is not an incomplete type), then the compiler knows
what to do in case of destruction. Regardless of whether the
constructor is user defined or not.

  I'm not exactly sure what you mean, but thinking about it, there might
not be any problem after all. Even if the class has no constructor,

Every class type has a constructor. Period.

that is, the situation is like this:

class ClassToBeManaged;
class AClass
    SmartPointer<ClassToBeManaged> ptr;

    // No constructor nor destructor defined here.

    // A function which allocates an instance of ClassToBeManaged and
    // gives it to 'ptr':
    void foo();

  Then as long as 'ClassToBeManaged' is fully declared when 'foo()' is
implemented, there should be no problem (as long as the assignment
operator of 'SmartPointer' is properly designed).

Correct. The only time you might have a problem is in a case

    class ClassToBeManaged ;
    ClassToBeManaged* factory() ;

    // ...
    SmartPointer< ClassToBeManaged > ptr( factory() ) ;

And as you say, good compilers will warn here.

James Kanze (GABI Software)
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